E3泛素连接酶RNF8在乳腺癌转移中的作用及机制研究

The epithelial to mesenchymal transition (EMT) contributes to tumor progression and has a critical role in the formation and development of metastasis. EMT is triggered by a diverse set of stimuli that can lead to stable reprogramming of epithelial cells to mesenchymal states; however, the underlying mechanism is remains elusive. RNF8 is an ubiquitin E3 ligase with C-terminal RING domain that can catalyze the formation of both K63- and K48-linked ubiquitin chains when coupled with distinct conjugating E2s. RNF8 plays essential roles in DNA damage response and spermatogenesis through mediating histone ubiquitination. Therefore, it is assumed that RNF8 might be also involved in the development and progression of tumor. However, whether and how RNF8 might be implicated in tumorigenesis is currently unkown. Recently, we found that ectopic expression of RNF8 in MCF-7 breast cancer cells could reduce the expression of E-Cadherin, a marker of epithelial, and inhibit cell migration; while depletion of RNF8 in MDA-MB-231 breast cancer cells led to the decrease of a mesenchymal marker, Vimentin, as well as the increase of E-Cadherin and promoted cell migration. More importantly, the expression of RNF8 is positively correlated with lymph node metastases in human breast cancer tissues. These results suggest that RNF8 is associated with EMT and breast cancer metastasis. This study is aimed to investigate the role of RNF8 in EMT and breast cancer metastasis, and to elucidate the underlying mechanism mediated by RNF8-dependent ubiquitination. This research will provide novel insight into the function of RNF8 and the molecular mechanism underlying RNF8-mediated metastasis. It will also have important implications in the development of novel potential targets for intervention of breast cancer metastasis.

肿瘤转移是一个多步骤多因素参与的复杂过程，其间上皮细胞向间质细胞的变迁(epithelial-mesenchymal transition, EMT) 本质上是一个细胞重编程和转分化的过程，组蛋白修饰等表观遗传学变化发挥重要作用。揭示EMT过程中细胞重编程的调控因素，对于阐明肿瘤转移机制具有重要意义。RNF8是一个泛素E3连接酶，通过对组蛋白进行泛素化修饰而在DNA损伤修复、精子发育中起重要作用，但是其在肿瘤转移中的作用尚不清楚。我们前期研究发现RNF8促进乳腺癌细胞EMT的发生，本项目拟在此基础上研究RNF8在EMT和乳腺癌转移中的作用；分离、鉴定RNF8与肿瘤转移相关的作用因子；阐明RNF8介导EMT和乳腺癌转移的分子机制。此项研究对于揭示RNF8的功能和乳腺癌转移具有重要意义，并将为针对RNF8的抗癌药物的研发提供新靶标。

上皮细胞向间质细胞的变迁(EMT)是肿瘤转移的关键一步，揭示EMT过程中细胞重编程的调控因素，对于阐明肿瘤转移机制具有重要意义。RNF8是一个泛素E3连接酶，在DNA损伤修复中发挥重要作用，但是其在肿瘤发生、发展、转移和耐药中的作用及机制尚不清楚。本项目利用过表达和敲低表达RNF8等技术手段，在细胞、动物和临床标本三个层面证实RNF8促进乳腺癌细胞EMT的发生，并促进乳腺癌的转移，RNF8的表达丰度与乳腺癌病人的预后负相关；通过进一步分离、鉴定RNF8的底物发现，RNF8与参与表观遗传调控的HDAC1相互作用，并影响其泛素化修饰水平；但如何影响EMT进程的机制研究还在继续进行中。此外，本项目还发现RNF8在肺鳞癌组织中特异性高表达；可以对AKT进行泛素化修饰而影响AKT的活化；并参与肺癌细胞对EGFR抑制剂等药物的耐药。本项目的研究结果表明RNF8在乳腺癌、肺癌的发生、转移和耐药过程中发挥重要作用，对于其机制的深入研究具有重要意义。本项目的研究结果提示RNF8是一个具有临床开发价值的靶标，体现在：一方面，在RNF8高表达的肿瘤中可以考虑联合应用PI3K/AKT的抑制剂进行治疗；另一方面，可以针对RNF8的E3泛素连接酶活性设计、开发相应的药物用于临床肿瘤的治疗。